Quantum Memories. A Review based on the European Integrated Project "Qubit Applications (QAP)"

Abstract

We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU Integrated Project "Qubit Applications". We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in "Qubit Applications" in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria.PACS. 03.67.-a Quantum information -03.67.Hk Quantum communication -03.67.Lx Quantum computation architectures and implementations -42.50.Ct Quantum description of interaction of light and matter; related experiments -42.50.Md Optical transient phenomena: quantum beats, photon echo, freeinduction decay, dephasings and revivals, optical nutation, and self-induced transparency 4 Criteria for assessing quantum memory performanceWe now discuss a number of evaluation criteria (figures of merit) and their relevance for different applications and implementations.

Control of quantum phenomena: Past, present, and future

“…One important area is coherent manipulation of quantum processes in solid-state systems, especially in semiconductor quantum structures [707,708]. Another potential application is optimal storage and retrieval of photonic states in atomic-vapor and solid-state quantum memories [358,359,[709][710][711][712][713][714]. The AFC methodology may be also applicable to physical problems where, instead of laser pulses, other means (e.g., voltages applied to an array of electrodes) are used to implement the control.…”

Characteristics of spectral-hole burning in Tm 3+ :YAG based on the perturbation theory

“…Spectral-hole burning (SHB) crystal material has been found to have a wide variety of applications, such as radio frequency (RF) signal processing, [1,2] optical memory, [3] quantum memories, [4] generating arbitrary wave form, [5,6] measuring optical frequency stability, [7] etc. Spectral-hole burning is a process by which spectrally varying absorption features are formed in material that contains inhomogeneously broadened absorbers.…”

Quantum Location Verification in Noisy Channels

“…This is especially the case since quantum memory is required for the most useful variants of the QLV protocol. The current experimental status regarding quantum memory is reviewed in [13] (see also [14]), where we learn that current timescales for successful storage of multipartite entangled states is in the order of milliseconds. Heroic efforts to increase such storage times to that required for workable large-scale quantum networks (i.e.…”

“…Heroic efforts to increase such storage times to that required for workable large-scale quantum networks (i.e. seconds) is currently underway in many laboratories [13]. The limiting factor in quantum memory is decoherence effects, where qubitenvironment interactions destroy the fragile entanglement of the quantum states.…”